Conventional control systems may include a plurality of field devices e.g., smart field devices positioned at various locations on a network. The smart field devices may include a processor, and can be temperature sensors, pressure sensors, flow rate sensors, valves, switches, etc. or combinations thereof. The smart field devices may be communicatively coupled to each other using an open smart communications protocol. Such open smart communications protocols may include HART®, PROFIBUS®, FOUNDATION® Fieldbus, etc. These open smart communications protocols enable smart field devices that are manufactured by different manufactures to be used together in the same control system (e.g., on the same network). The conventional control systems also may include a controller communicatively coupled to each of the smart field devices using the open smart communications protocol. Moreover, the controller may receive data from each of the smart field devices.
In operation, each smart field device can perform a function on the network. For example, a temperature sensor may measure a temperature of a liquid, a pressure sensor may measure pressure within a container, a flow rate sensor may measure a flow rate of the liquid, etc. Similarly, valves and switches may be opened to allow or increase the flow of the liquid, or can be closed to stop the flow of the liquid or decrease the flow rate of the liquid. After the smart field devices obtain measurements of various process parameters, or after the valves or switches are opened/closed, the smart field devices may communicate with the controller. For example, the smart field devices may forward code which includes the data to the controller, and the controller can implement a control procedure on the network based on the received code.
Specifically, in the conventional control systems, the controller can be adapted to configure and/or monitor the field devices using the Foundation Fieldbus Function Block language, in which each function block is a subroutine of an overall control procedure. Such controller operates in conjunction with other function blocks to implement control loops within the network. Alternatively, the controller can be adapted to implement the control procedure using an IEC 61131-x language, such as a Ladder Logic language, Sequential Function Chart language, Instruction List language, etc. When the Ladder Logic language is used, the controller is configured to implement the control process procedure based on a plurality of horizontal Ladder Logic statements referred to as “rungs.” Each rung defines a relationship between variables, such as between an output variable and an input variable. For example, a simple rung may indicate that a particular output variable is “ON” if variables A and B also are turned “ON.” For example, the Ladder Logic programs may be expressed in terms of Ladder Logic graphs that include input symbols, line segments, and output symbols. A complete ladder logic program may be recorded on a magnetic tape or disk, and subsequently may be uploaded to a memory of the controller.
Nevertheless, in the conventional control systems, in order to implement the control procedure on the network, each of the devices in such system must be configured using the same programming language. For example, the controller and each of the field devices can be configured using the Ladder Logic language. The Ladder Logic language may be usable for implementing binary logic within the network. However, the Ladder Logic language may not be usable for implementing an analog control within the network.